Small spherical flame ~
Today, I saw that Physics Girl did a very interesting experiment: fix the camera equipment and a lit candle in a small basically closed box, and then throw the box down from upstairs.
Why are you doing this? In fact, it is to record the moment when the flame becomes spherical in weightlessness:
usually the flame we see is upward, for example, the flame of a candle is an upward elongated "teardrop". This shape comes from the convection of air: the hot air in the flame rises, the cold air next to it is replenished, and the rise of hot air depends on gravity. In weightlessness (in space, or in free fall), without such convection, the flame becomes a small sphere.
in space, astronauts have also done some research on combustion and flame. they ignite small drops of heptane in special equipment and then observe the performance of the flame. They found that lower-temperature flames are formed in microgravity, and the products of the combustion reaction are different from those on the ground. The following dynamic picture is an ignition experiment in a weightlessness environment:
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but it is very difficult to lose weight by throwing boxes, after all, the time is very short, even with high-speed photography, the spherical flame can be seen is also very short. If you want to throw it to a very high place for a long time, it is also dangerous. You'd better not imitate the full version of
Physics Girl video: https://www.youtube.com/watch?v=VAA_dNq_-8c